Since Election Day, President-elect Barack Obama and his team have focused on the transition of power, appointing Cabinet officers and key staff in preparation for the first day of the Obama administration.
But perhaps the trickiest part of that transition will occur today behind the scenes with the physical changing of the guard -- the frantic five-hour period in which the Bush family moves out of the White House and the Obama family moves in.
Former White House usher Gary Walters describes the move in and out of the 132-room mansion as "a very well organized ballet choreography."
"The concept is when [the Obamas] walk in after the reviewing stand that they walk into their new home. Their clothes are in the closets, their favorite foods are in the pantry, the furniture that they have designated to be in certain locations is there," said Walters, who has worked on five presidential move-ins.
Brad Blakeman, a former deputy assistant to President Bush and gatekeeper of the president's schedule in 2001 called it a "military precision operation because you are working against the clock.
"Within the six hours that the parade and swearing-in take place, the White House and West Wing will be totally transformed to receive the new president and his family," Blakeman said.
The Obama family will make the short drive across Pennsylvania Avenue from Blair House, where they are staying, and arrive at the White House around 10:30 a.m.
President Bush and first lady Laura Bush will greet the Obamas at the North Portico entrance and escort them inside to have coffee with the family and some senior staff. When it's time to head to Capitol Hill for the swearing-in, the president and president-elect ride together, alone, in the presidential limo while the first lady and Michelle Obama ride in a separate car behind them.
Once those limos leave the White House grounds, the clock starts ticking.
At about the time that they leave, moving vans filled with the Obamas' possessions brought from Chicago will line up at the Southwest Gate to the White House. The Obamas are responsible for getting their things to this point, but once the trucks reach the White House door, the residence staff takes over for privacy and security reasons.
When the Obamas and Bushes finish their coffee and their motorcade heads for the inaugural ceremony about 11 a.m., the trucks will be waved onto the grounds, and the race against time begins.
The rooms will be stripped of whatever belonged to the Bushes and where necessary, will be repainted, and the Obamas' belongings and furniture will be installed. The movers will be keeping an eye on the clock, because they only have until the last marching band in the inauguration parade passes the reviewing stand before the Obamas walk into their new home, sometime between 4 p.m. and 6 p.m.
Walters said he had a team of about 95 people working nonstop on Inauguration Day to make sure the transition is smooth and complete.
"The choreography is planned almost down to the minute," Walters said.
That planning includes a division of labor so precise that no job overlaps and no time is wasted. Staff is divided into who is carrying furniture in, who is carrying it out, who unpacks the boxes and puts things away, and who takes the empty ones out. Walters said there is even a staffer assigned to operate the elevator because otherwise things could get backed up.
The goal at the end?
"There are no empty or partially empty boxes in corners, everything is put away where it's supposed to be so they can be in their new home," Walters said.
Michelle Obama and her staff have been working with the White House Ushers Office to determine what needs to be unpacked immediately and where they would like things to go. The Obamas can choose to replace furniture that the Bushes had in the residence or supplement it with items from the White House collection. Walters said the Ushers Office will propose a floor plan to members of the new first family and ask if they want to keep things as they are or make changes. The Obamas work with the White House curator's office to select artwork that they would like to display.
Today's moving ordeal may not be so tricky, because the Bushes packed up early and shipped much of their belongings to Texas.
The only personal piece of furniture they will be taking with them is a chest of drawers that belonged to Bush's grandmother.
"Mrs. Bush did express that she knew when she moved here that she would have lovely historic pieces to choose from so she did not bring a lot of furniture," said Sally McDonough, communications director for the first lady.
When he moved into his new office in 2001, Bush brought with him several paintings of Texas that were borrowed from museums in his home state, including one of the Alamo by Julian Onderdonk and a landscape of Texas bluebonnets by Onderdonk. Bush also hung a painting of western horse riders called "A Charge to Keep" by W.H.D. Koerner because it reminded him of a book of the same title.
In one of his first decisions in office, Bush commissioned a new rug for the Oval Office, oval shaped with a sunburst design that he was quite fond of talking about with world leaders who visited. Laura Bush designed the rug, following instructions from her husband that he wanted something optimistic.
Obama senior adviser Valerie Jarrett said the president-elect "loves" the rug but said it was too early to think about redecorating the Oval Office.
There will be a not-so-secret surprise waiting for Obama when he sits down in the Oval Office for the first time as president. Tradition holds that the outgoing president leaves a note for the incoming president in the top drawer of the desk, the contents of which are never released publicly.
White House aides have been working with the archivist and other government officials to make sure that records are being kept and organized.
There is a picture gallery on the wall outside the Cabinet Room that includes a rotating collection of photographs of the president.
As recently as last week, that gallery showed photographs of Bush with about a dozen world leaders -- some of his closest allies such as former British Prime Minister Tony Blair, German Chancellor Angela Merkel and Indian Prime Minister Manmohan Singh.
It is expected that photographs of Obama will quickly be swapped in Tuesday, and will perhaps include images from the inaugural ceremonies.
ABC News' Ann Compton contributed to this report.